I have just been playing with the HG612 as I now have two of them, ready for my (seemingly never going to happen as it still can't be ordered) Zen fibre going live.

While fiddling with VLANs so I could use them both via a single WAN port on my router, I have confirmed that you CAN have both the WAN and LAN of the HG612 out of a single ethernet port. I never tried on Digital Region because my WAN speed was so close to the port speed I didn't want the overhead of the HG612 LAN traffic potentially slowing things down. However as BT is capped at 80Mbit (yeah, I'm only seeing 66Mbit so far), it seems unlikely this would ever be an issue, plus it was even more useful now I would be saving TWO ethernet cables not just one.

Basically, I configured WAN to VLAN 2 for one HG612, VLAN 3 for the other, but left both ports unticked for port binding (normally LAN1 is ticked). This allows all traffic to go out of either port and as the WAN traffic is tagged to their own VLAN each, this can be specified on the router to determine which connection should be routed to which modem.

My router is set to establish PPPoE on eth1.2 for Origin and eth1.3 for Zen, and bridge eth1 to the LAN. As I understand it, that means it will only send untagged traffic on eth1 to the LAN and vice versa, thus maintaining isolation.

Interestingly this also means that technically you could just plug the HG612 into the LAN directly and have a router with only a single ethernet port. It would be a bit of a waste of LAN bandwidth though as all Internet traffic would be going across twice, plus it depends on if your LAN switch supports passing VLAN tags or not.